Routine vaccination has dramatically decreased the incidence of many serious diseases, and new vaccines are becoming available to improve the quality of health care. Vaccination programs are a cornerstone of modern public health, and are of central importance in preparedness for dealing with potential health emergencies, such as the recurrence of pandemic influenza. Public and professional confidence in vaccination depends on reliable post-marketing surveillance systems to ensure that rare and unexpected adverse effects are rapidly identified. Our goal is to improve the quality of vaccination programs by improving the quality of physician adverse vaccine event detection and reporting to the national Vaccine Adverse Event Reporting System (VAERS). Electronic medical records available from all ambulatory care encounters in a large multi-specialty practice will be used. Every patient receiving a vaccine will be automatically identified, and for the next 30 days their health care diagnostic codes, laboratory tests, and medication prescriptions will be evaluated for values suggestive of an adverse event. When a possible adverse event is detected it will be recorded, and the appropriate clinician will be notified electronically. Clinicians will be able to preview a pre-populated report with information from the electronic medical record about the patient, including vaccine type, lot number, and possible adverse effect, to inform their clinical judgment about whether they wish to send a report. Clinicians will have the option of adding free-text comments to pre-populated VAERS reports or to document their decision not to send a report. Approved reports will be securely transferred to VAERS as electronic messages in an interoperable health data exchange format (HL7). We will evaluate the system by comparing adverse event findings to those in the Vaccine Safety Datalink project and in a randomized trial to test the hypothesis that the combination of secure, computer-assisted, clinician approved, adverse event detection and automated electronic reporting will substantially increase the number, completeness, validity and timeliness of physician approved case reports to VAERS compared to the existing spontaneous reporting system. [unreadable] [unreadable] [unreadable] [unreadable]